Alternator pulley unit with a built-in one-way clutch

ABSTRACT

One-way clutch  18  has a spring the elastic modulus of which is limited up to a predetermined value, seal rings  36   a,    36   b  have a sliding resistance with respect to the inner rings  22  which is limited up to a predetermined value, and support bearings  17   a,    17   b  have a rotation resistance which is limited up to a predetermined value. The torque required to rotate the driven pulley  7   a  relative to the sleeve  8   a  in the direction for overrun condition is limited up to 0.5N·m. Accordingly, the power generating efficiency of the alternator is secured while abnormal sounds are prevented from occurring with the life of endless belt being prevented from reducing.

FIELD OF THE INVENTION

An alternator pulley unit with a built-in one-way clutch of the presentinvention is utilized for driving an alternator serving as a generatorfor vehicles, by fixing the pulley unit to an end of a rotation shaft ofthe alternator, and spanning an endless belt between the pulley unit anda drive pulley fixed to an end of a crank shaft of an engine.

BACKGROUND OF THE INVENTION

A structure of an alternator for generating electric power required foran automobile using the automobile propulsion engine as a drive sourceis described for example in Japanese Patent Publication No. TokukaiHei7-139550. FIG. 5 shows the alternator described in this Application.A rotation shaft 3 is rotatably supported inside a housing 2 by a pairof rolling bearings 4. A rotor 5 and a commutator 6 are disposed on anintermediate part of the rotation shaft 3. In addition, a driven pulley7 is fixed to a portion protruding toward the outside of the housing 2,at one end (the right end in FIG. 5) of the rotation shaft 3. In thecondition where it is assembled into an engine, an endless belt isspanned around the driven pulley 7, and the rotation shaft 3 is freelyrotated by the engine crank shaft.

For the above described driven pulley 7, one which is simply fixed tothe rotation shaft 3 has heretofore been used. On the other hand,various kinds of alternator pulley unit with a built-in one-way clutchhave been proposed and used in part, such as one in which when therunning speed of the endless belt is constant or tends to increase,motive power is freely transmitted from the endless belt to the rotationshaft, while when the running speed of the endless belt tends todecrease, the driven pulley and the rotation shaft are freely rotatablerelative to each other. An alternator pulley unit with a built-inone-way clutch having functions described above, is described forexample in Japanese Patent Publication Nos. Tokukai Sho56-101353,Tokukai Hei7-3178807, Tokukai Hei8-61443, Tokukai Hei10-285873, JapanesePatent Publication No. Tokuko Hei 7-72585, France Patent Publication No.FR2726059A1 and the like. Moreover, such an alternator pulley unit witha built-in one-way clutch has been actually used in part.

FIG. 6 shows an alternator pulley unit with a built-in one-way clutchdescribed in Japanese Patent Publication No. Tokukai Hei10-285873. Thisalternator pulley unit with a built-in one-way clutch has a sleeve 8that can be freely externally fitted and secured to a rotation shaft 3(FIG. 5). A driven pulley 7 a is then disposed concentric with thesleeve 8 around the sleeve 8. In addition, a pair of support bearings 9and a one-way clutch 10 are provided between an outer peripheral face ofthe sleeve 8 and an inner peripheral face of the driven pulley 7 a. Ofthese, the support bearings 9 enable free rotation of the sleeve 8 andthe driven pulley 7 a relative to each other, while rotatably supportinga radial load applied to the driven pulley 7 a.

Moreover, the one-way clutch 10 can transmit a turning force from thedriven pulley 7 a to the sleeve 8 only when the driven pulley 7 a has atendency to rotate in a predetermined direction relative to the sleeve8. Therefore, to construct the aforementioned one-way clutch 10, a camface 12 is formed on an outer peripheral face of an intermediate portionof an inner ring 11 which is externally fitted and secured to the sleeve8. Furthermore a plurality of rollers 13 are arranged between the outerperipheral face of the cam face 12 and the inner peripheral face of thedriven pulley 7 a. Then, between these rollers 13 and a retainer 14 forretaining these rollers 13, there are provided a plurality of springs(not shown). These springs resiliently press the respective rollers 13in a direction to make the respective rollers 13 encroach into a wedgeshape at a portion where, of the dimensions of a cylindrical gap formedbetween the outer peripheral face of the cam face 12 and the innerperipheral face of the driven pulley 7 a, the width across thediametrical direction becomes narrow. Furthermore, a torque for pressingthe respective rollers 13 based on the resilience is designated as 4N·mor less.

According to the alternator pulley unit with a built-in one-way clutchdescribed in the above described Japanese Patent Publication No. TokukaiHei10-285873 constituted as described above, generating efficiency ofthe alternator can be ensured to some degree. That is to say, when therotational speed of the engine increases, and the running speed of theendless belt 15 spanning between the drive pulley and the driven pulley7 a tends to increase, there is a tendency for the driven pulley 7 a torotate relative to the sleeve 8 in a predetermined direction. As aresult, the respective rollers 13 encroach into the wedge shape (becomelocked) at the portion where, of dimensions of the cylindrical gapformed between the outer peripheral face of the inner ring 11 and theinner peripheral face of the driven pulley 7 a, the width across thediametral direction becomes narrow, thereby enabling free transmissionof the turning force from the driven pulley 7 a to the rotation shaft 3.On the other hand, when the rotational speed of the engine decreases,and the running speed of the endless belt 15 tends to decrease, thedriven pulley 7 a rotates relative to the sleeve 8 in the directionopposite to the above described predetermined direction. Therefore, therespective rollers 13 shift to a portion where the width of the abovedescribed cylindrical gap becomes wider, enabling free rolling of theserespective rollers 13 in the concerned portion (giving an overrunstate), so that the driven pulley 7 a and the rotation shaft 3 canfreely rotate relative to each other. At this time, since the respectiverollers 13 are pressed by means of a torque of 4N·m or less based on theresilience of the aforesaid respective springs, shift from the lockedstate to the overturn state can be performed at a relatively early stagefrom when the running speed of the endless belt 15 starts to decrease.Since the shift to the overrun state is performed at a relatively earlystage as described above, the rotation shaft 3 of the alternator cancontinue to rotate in a high region to some extent based on its ownrotational force of inertia, regardless of variations in the rotationalspeed of the engine, sot hat the power generating efficiency of thealternator can be ensured to some degree.

In the case of the alternator pulley unit with a built-in one-way clutchdescribed in Japanese Patent Publication No. Tokukai Hei10-285873constituted and operated as described above, it still cannot be saidthat the power generating efficiency is sufficiently ensured. Inaddition, there is the possibility of the occurrence of abnormal soundsdue to rubbing of the driven pulley 7 a and the endless belt 15 againsteach other, and a decrease in the life span of the endless belt 15cannot be sufficiently prevented. That is to say, since the crank shaftis rotated and driven based on intermittent explosions inside the enginecylinder, completely smooth rotational motion is not performed, and theturning angular velocity varies slightly even during one rotation. Thevariation in the turning angular velocity increases as the rotationalspeed of the engine decreases. As a result, the running speed of theendless belt 15 spanning to the drive pulley secured at the end of thecrank shaft also varies slightly. Therefore, to ensure sufficient powergenerating efficiency of the alternator, it is necessary to make thepulley unit follow the slight variations in the running speed of theendless belt 15, and to promptly perform the shift from the locked stateto the overrun state when the running speed of the endless belt 15 tendsto decrease.

On the other hand, even if the running speed of the endless belt 15varies slightly as described above, the rotation shaft 3 of thealternator rotated and driven via the driven pulley 7 a by the endlessbelt 15 does not vary so abruptly, based on the rotational force ofinertia of the rotation shaft 3, and the rotor 5 and the commutator 6secured to the rotation shaft 3. Hence, there is a tendency for theinner peripheral face of the endless belt 15 and the outer peripheralface of the driven pulley 7 a to rub against each other in oppositedirections. As a result, a stress in different directions actsrepeatedly on the endless belt 15 which is rubbed against the drivenpulley 7 a, so that slipping occurs between the endless belt 15 and thedriven pulley 7 a. Hence, abnormal sounds are likely to occur due tothis slipping, or the lift span of the endless belt 15 is shortened.

The decrease in life span of the endless belt 15 based on the frictionbetween the outer peripheral face of the driven pulley 7 a and the innerperipheral face of the endless belt 15 as described above actuallyarises also due to repeated acceleration and deceleration at the time oftraveling. That is to say, at the time of acceleration, a drive force istransmitted from the endless belt 15 to the driven pulley 7 a, while onthe contrary, at the time of deceleration, a braking force acts from theendless belt 15 on the driven pulley 7 a that tends to continue rotationbased on the inertia described above. The braking force and the abovedescribed drive force act on the inner peripheral face of the endlessbelt 15 as a frictional force in opposite directions, resulting in adecrease in the life span of the endless belt 15. In particular, in thecase of a vehicle provided with an exhaust brake such as a truck, thedeceleration at the time of decreasing rotation of the crank shaft inthe accelerator-off state is considerable. Based on the above describedbraking force, a frictional force applied on the inner peripheral faceof the endless belt 15 increases, and as a result, the life spandecreases noticeably.

To solve the various problems described above, it has been heretoforeproposed to use a pulley with a built-in one-way clutch as the pulleyfor an alternator. In the case of the structure described in theaforementioned Japanese Patent Publication No. Tokukai Hei10-285873however, the torque for pressing the respective rollers 13 constitutingthe one-way clutch 10 in a predetermined direction is as large as 4N·m.Therefore, the structure described in Japanese Patent Publication No.Tokukai Hei10-285873 can cope with a relatively large variation in therotational speed of the engine, but it is unlikely to cope with slightvariations in the turning angular velocity occurring during one rotationof the crank shaft. If the pulley unit cannot cope with slightvariations in the turning angular velocity of the crank shaft, then notonly can the rotation of the rotation shaft 3 of the alternator not bemaintained in a high rotation region, but also stress in oppositedirections acts repeatedly on the endless belt 15 which is rubbedagainst the driven pulley 7 a as described above. As a result, there isa possibility that the power generating efficiency of the alternatorcannot be sufficiently ensured, or that the occurrence of abnormalsounds due to slipping between the endless belt 15 and the driven pulley7 a, and a decrease in the life span of the endless belt 15 cannot besufficiently prevented.

Moreover, in the case of the alternator pulley unit with a built-inone-way clutch described in Japanese Patent Publication No. TokukaiHei10-285873, only the size of a torque for pressing the respectiverollers 13 constituting the one-way clutch 10 in a predetermineddirection is addressed to ensure the power generating efficiency, andthis torque value is designated as 4N·m or less. However, when therunning speed of the endless belt 15 tends to decrease, and it isnecessary to rotate the driven pulley 7 a relative to the rotation shaft3 of the alternator in the direction to give overrun, not only does thetorque for pressing the respective rollers 13 in the predetermineddirection become an actual resistance to the rotation, but also therolling rotation resistance of the respective support bearings 9disposed on opposite sides of the one-way clutch 10, and the slidingresistance of seal members disposed between the driven pulley 7 a andthe sleeve 8 which are attached to end portions of the respectivesupport bearings 9 becomes an actual resistance to the rotation.Therefore, in the case of the conventional structure described inJapanese Patent Publication No. Tokukai Hei10-285873, the torquenecessary to rotate the driven pulley 7 a relative to the rotation shaft3 of the alternator in the direction to give overrun, actually increasesto larger than 4N·m. When in this way the torque increases, the torquewhich becomes a resistance against rotation in the direction to giveoverrun, suppresses the rotation based on the rotational force ofinertia of the rotation shaft 3 or the like. Therefore it becomes moredifficult to sufficiently ensure the power generating efficiency of thealternator, or to sufficiently prevent the occurrence of abnormal soundsdue to slipping between the endless belt 15 and the driven pulley 7 a,and a decrease in the life span of the endless belt 15.

SUMMARY OF THE INVENTION

In view of the above situation, the present invention has been developedfor ensuring the power generating efficiency of the alternator andpreventing the occurrence of abnormal sounds and a decrease in the lifespan of the endless belt.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of one half of a first example of theembodiment of the present invention.

FIG. 2 is a cross sectional view taken along the line II—II of FIG. 1 toshow only a one-way clutch.

FIG. 3 is a cross sectional view of one half of a second example of theembodiment of the present invention.

FIG. 4 is a cross sectional view of one half of a third example of theembodiment of the present invention.

FIG. 5 is a cross sectional view of one example of the conventionalalternator.

FIG. 6 is a cross sectional view of one example of the conventionalalternator pulley unit with a built-in one-way clutch.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An alternator pulley unit with a built-in one-way clutch of the presentinvention comprises, as with the alternator pulley with a built-inone-way clutch heretofore known: a sleeve that can be freely externallyfitted and secured to a rotation shaft of the alternator, a drivenpulley disposed concentric with the sleeve around the sleeve; a one-wayclutch provided between an axially intermediate portion on an outerperipheral face of the sleeve and an axially intermediate portion on aninner peripheral face of the driven pulley, which can freely transmit aturning force between the driven pulley and the sleeve, only when thedriven pulley tends to rotate relative to the sleeve in a predetermineddirection; and a pair of support bearings provided between the outerperipheral face of the sleeve and the inner peripheral face of thedriven pulley to hold the one-way clutch from the axially oppositesides, which enable free rotation of the sleeve and the driven pulleyrelative to each other, while rotatably supporting a radial load appliedto the driven pulley.

In particular, according to the alternator pulley unit with a built-inone-way clutch of the present invention, a torque necessary for rotatingthe driven pulley relative to the sleeve in the direction opposite tothe predetermined direction is limited up to 0.5N·m, and morepreferably, 0.3N·m or less.

In the case of the alternator pulley unit with a built-in one-way clutchof the present invention constructed as described above, a torquenecessary for rotating the driven pulley relative to the sleeve in thedirection opposite to the predetermined direction is limited up to0.5N·m (preferably 0.3N·m or less). Therefore, the alternator pulleyunit with a built-in one-way clutch of the present invention cansufficiently cope with slight variations in turning angular velocity, sothat when the running speed of the endless belt spanning to the drivenpulley tends to decrease, the driven pulley and the rotation shaft ofthe alternator can be promptly and freely rotated relative to eachother. As a result, according to the present invention, the powergenerating efficiency of the alternator can be sufficiently ensured, andthe occurrence of abnormal sounds and a decrease in the life span of theendless belt can be sufficiently prevented.

To clarify the grounds from which the above described effects can beobtained by the alternator pulley unit with a built-in one-way clutch ofthe present invention, a description is given of a test performed by thepresent inventor. At first, in performing this test, four kinds ofalternator pulley units with a built-in one-way clutch heretofore beinggenerally used, were prepared wherein a minimum torque required forrotating the driven pulley relative to the sleeve in the directionopposite to a predetermined direction (in the direction to give overrun)was changed in the range of from 0.3 to 0.6N·m. The test was performedby confirming whether or not the respective pulley unit could followslight variations in the turning angular velocity occurring during onerotation of the crank shaft, using a stroboscope. Moreover, therotational speed of the driven pulley was designated as 11,500±80 rpm.Variations in the turning angular velocity occurring during one rotationof the crank shaft were applied by providing a universal joint betweenthe drive pulley and a drive shaft for driving the drive pulley. Inaddition, the current load of the alternator was designated as 50A. Theresults of the test performed in this manner are shown in Table 1.

TABLE 1 Minimum Torque required for Overrun Condition Initial BeltTension (N · m) (Kgf) 0.3 0.4 0.5 0.6 90 ◯ ◯ ◯ X 70 ◯ ◯ ◯ X 50 ◯ ◯ X X30 ◯ X X X

In Table 1, O denotes that the pulley unit could follow the variationsin the turning angular velocity occurring during one rotation of thecrank shaft, and rotation of the driven pulley and the sleeve occurredrelative to each other, while x denotes that the pulley unit could notfollow the variations in the turning angular velocity, and rotation ofthe driven pulley and the sleeve did not occur relative to each other.As seen from the test results shown in Table 1, in order to make thepulley unit capable of following the variations in the turning angularvelocity when the tension of the endless belt is set to 70 kgf, it isrequired to set the torque necessary for rotating the driven pulleyrelative to the sleeve in the direction to give overrun, to 0.5N·m orless. Incidentally, the tension of the endless belt is generally set toabout 70 kgf. On the other hand, in the case of an actual automobileengine, even if the tension of the endless belt is initially set to 70kgf, the endless belt itself causes changes with the lapse of time suchas a permanent deformation or the like, and as a result there is thepossibility that the tension of the endless belt may decrease to about30 kgf. Therefore, even if the tension of the endless belt decreases toabout 30 kgf, it is preferable that the pulley unit can follow thevariations in the above described turning angular velocity. As seen fromthe test results shown in Table 1, in order to make it possible for thepulley unit to follow the variations in the turning angular velocity,even if the tension of the endless belt decreases to about 30 kgf, it isrequired to set the torque necessary for rotating the driven pulleyrelative to the sleeve in the direction to give overrun, to 0.3N·m orless. As seen from the test results shown in Table 1, in the case of thepresent invention, the pulley unit can sufficiently cope with slightvariations in the turning angular velocity occurring during one rotationof the crank shaft, to ensure that the power generating efficiency ofthe alternator, and the occurrence of abnormal sounds and a decrease inthe life span of the endless belt can be sufficiently prevented.

FIG. 1 and FIG. 2 show a first example of an embodiment of the presentinvention. An alternator pulley unit with a built-in one-way clutch inthis example is formed in an overall cylindrical shape, and comprises asleeve 8 a externally fitted and secured to an end of a rotation shaft 3(see FIG. 5) of an alternator, and a driven pulley 7 a disposedconcentric with the sleeve 8 a around the sleeve 8 a. Of these, thesleeve 8 a is freely rotatable together with the rotation shaft 3.Therefore, in the illustrated example, a female spline portion 16 isformed on an inner peripheral face at an intermediate portion of thesleeve 8 a, so as to be freely engageable with a male spline (not shown)formed on an outer peripheral face at an end of the rotation shaft 3.Here, instead of using the spline, the structure for preventing rotationof the rotation shaft 3 and the sleeve 8 a relative to each other mayinvolve a screw, the fitting of non-cylindrical faces to each other, orconnection by a key or the like.

The driven pulley 7 a disposed around the sleeve 8 a described above ismounted with support bearings 17 a, 17 b described below and a one-wayclutch 18 on the inside thereof. On the outer peripheral face of thedriven pulley 7 a, there are formed a plurality of recesses 19 (four inthis case) parallel to each other and over the whole periphery thereof,with the respective sections being in a V-shape. An endless belt 15 (seeFIG. 6) spanning between such a driven pulley 7 a and a drive pulley(not shown) is provided wherein a plurality of ribs (four in this case)are formed continuously over the whole inner periphery, with therespective sections being in a V-shape.

Between the outer peripheral face of the sleeve 8 a constituted asdescribed above and the inner peripheral face of the driven pulley 7 aconstituted as described above, there are provided the pair of supportbearings 17 a, 17 b, respectively being radial roller bearings, and aone-way clutch 18 being a roller clutch. To constitute the one-wayclutch 18 of these, an inner ring 20 for the one-way clutch isexternally fitted and secured by interference fit to the outerperipheral face in the intermediate portion of the sleeve 8 a. The innerring 20 for the one-way clutch is formed in an overall cylindrical shapefrom a plate material made of a hard metal such as bearing steel or thelike, or a plate material of steel for carburizing such as SCM 415 orthe like, with the outer peripheral face being a cam face 21 describedlater.

Moreover, to construct the respective support bearings 17 a, 17 b, innerrings 22 are respectively externally fitted and secured by interferencefit to the outer peripheral face of the sleeve 8 a at opposite ends.These respective inner rings 22 which are similarly formed from a platematerial made of a hard metal such as bearing steel or the like, or aplate material of steel for carburizing such as SCM 415 or the like, areeach formed in an overall cylindrical shape to give an L-shape incross-section, by forming an inner ring side brim portion 24 in aradially outwards oriented flange shape at one end rim of a cylindricalportion 23.

These inner rings 22 are externally fitted to the sleeve 8 a with theinner ring side brim portions 24 located at opposite sides to eachother, and with end rims thereof respectively abutted against axiallyopposite end portions of the inner ring 20 for the one-way clutch. Inthis case, the outer diameter of the cylindrical portion 23 of therespective inner rings 22 is made larger than that of an inscribedcircle related to the bottom portion of a plurality of recesses 25formed on the outer peripheral face of the inner ring 20 for the one-wayclutch.

On the other hand, an outer ring 26 is internally fitted and secured byinterference fit to the driven pulley 7 a. The outer ring 26 serves notonly as an outer ring for the one-way clutch 18, but also as an outerring for the respective support bearings 17 a, 17 b, and is also formedin an overall cylindrical shape by subjecting a plate material made of ahard metal such as bearing steel or the like, or a plate material ofsteel for carburizing such as SCM 415 or the like to press working. Suchan outer ring 26 is formed with outer ring side brim portions 27 a, 27b, respectively in a radially inwards oriented flange shape, at axiallyopposite end portions. Here, of these outer ring side brim portions 27a, 27 b, one outer ring side brim portion 27 a (left side in FIG. 1) hasa thickness similar to that of the body portion of the outer ring 26because of being formed prior to the assembly of the other constituentmembers. On the other hand, the other outer ring side brim portion 27 b(right side in FIG. 1) is made thin because of being formed afterassembly of the other constituent members.

Then, the one-way clutch 18 is constructed including the innerperipheral face of the intermediate portion of the outer ring 26 and theouter peripheral face of the inner ring 20 for the one-way clutch. Thatis to say, in a plurality of places on the outer peripheral face of theinner ring 20 for the one-way clutch, there are formed respectiverecesses 25, referred to as ramps, whose depths increase towards onecircumferential end side (the right side in FIG. 2), axially over theinner ring 20 for the one-way clutch, and at equal spacingcircumferentially to each other, with the outer peripheral face of theinner ring 20 for the one-way clutch being the cam face 21. Between theouter peripheral face of the inner ring 20 for the one-way clutch ad theinner peripheral face of the outer ring 26, there is formed acylindrical gap 28. Of the dimensions of the cylindrical gap 28, theheight in cross-section related to the diametral direction of the outerring 26 is larger than the outer diameter of the plurality of rollers 29disposed inside the cylindrical gap 28, in portions corresponding to therespective recesses 25, and in portions away from the respectiverecesses 25, is smaller than the outer diameter of the respectiverollers 29.

Moreover, the one-way clutch 18 is respectively provided with a clutchretainer 30 formed in a cylindrical cage shape from a synthetic resin,and a plurality of rollers 29 and springs 39, between the innerperipheral face in the intermediate portion of the outer ring 26 and theouter peripheral face of the inner ring 20 for the one-way clutch. Ofthese, the clutch retainer 30 is mounted inside the outer ring 26, withrotation thereof relative to the inner ring 20 for the one-way clutchbeing made impossible, by making protrusions 31 formed on the innerperipheral face engage with the recesses 25 formed on the outerperipheral face of the inner ring 20 for the one-way clutch. Inaddition, one axial face of the protrusions 31 is made to face the endrim of respective inner rings 22, thereby preventing the clutch retainer30 from shifting axially. The plurality of rollers 29 are held insidepockets 32 formed in the clutch retainer 30, with rolling and somecircumferential displacement being made possible.

The respective springs 39 are also disposed between pillar portions 40constituting the clutch retainer 30 as described above and therespective rollers 29, to resiliently press the respective rollers 29circumferentially in the same direction (in the leftward direction inFIG. 2). Here, the respective springs 39 are generally plate springsmade of stainless steel by bending back a strip-form spring plate in aU-shape or a V-shape, or synthetic resin springs formed integrally withthe retainer.

The respective support bearings 17 a, 17 b comprise the respective innerrings 22 and portions near the axially opposite ends of the outer ring26. That is to say, between the outer peripheral face of the respectiveinner rings 22 and the inner peripheral face of portions near theaxially opposite ends of the outer ring 26, there are disposed bearingretainers 33 formed in a cylindrical cage shape from a synthetic resin,and a plurality of rollers 34 held so as to be freely rollable by thebearing retainers 33, to thereby form radial roller bearings.

Furthermore, between the outside face of the outer ring side brimportions 27 a, 27 b and the inside face of the inner ring side brimportions 24, there are respectively mounted floating washers 35, freelyrotatable relative to the respective outer ring side brim portions 27 a,27 b and the inner ring side brim portions 24. The respective floatingwashers 35 are formed in a ring shape from metals having aself-lubricating property such as copper or the like, metals subjectedto tufftriding, metal materials impregnated with a lubricating oil suchas porous metal or the like, or synthetic resins having a lowcoefficient of friction such as polyamide resin, polyacetal resin,polytetrafluoroethylene resin or the like. These floating washers 35 areloosely inserted between the outer ring side brim portions 27 a, 27 band the inner ring side brim portions 24. The floating washers 35 areguided (kept from displacement in the radial direction) by the outerperipheral faces of the respective inner rings 22 and the innerperipheral face of the driven pulley 7 a.

Moreover, gaps between the inner peripheral face at the axially oppositeend portions of the outer ring 26 and the outer peripheral face of therespective inner rings 22 are respectively covered with seal rings 36 a,36 b. These seal rings 36 a, 36 b respectively comprise a metal core 37and a resilient member 38, and are internally fitted and supported onthe inner peripheral face at opposite end portions of the outer ring 26with the outer diameter of the resilient member 38 being resilientlyreduced. Edge rims of a plurality of seal lips respectively provided oneach resilient member 38 are then slidingly contacted with or abuttedagainst the outer peripheral faces of the intermediate portions of theinner rings 22 and the inside faces of the respective outer ring sidebrim portions 27 a, 27 b. Here, in the case of this example, the oneedge rim of one seal ring 36 a (the left one in FIG. 1) of therespective seal rings 36 a, 36 b is slidingly contacted or abuttedagainst the inside face of one outer ring side brim portion 27 a, sothat positioning in the axial direction of one seal ring 36 a relativeto the outer ring 26 is effected. On the other hand, of the respectiveseal rings 36 a, 36 b, one edge rim of the other seal ring 36 b (theright one in FIG. 1) is abutted against a stepped face between the otherouter ring side brim portion 27 b and the body portion of the outer ring26. Concurrently, the other end rim of the other seal ring 36 b isslidingly contacted with or abutted against the inside face of the otherouter ring side brim portion 27 b, thereby effecting positioning in theaxial direction of the other seal ring 36 b relative to the outer ring26.

Furthermore, portions on one side face of the metal cores 37 of therespective seal rings 36 a, 36 b facing the end face of the bearingretainers 33 constituting the respective support bearings 17 a, 17 b arearranged so as not to be covered by the resilient members 38, so thateven if the end faces of the bearing retainers 33 and the one side facesof the metal cores 37 are slidingly contact with each other, the slidingresistance an be kept low.

In particular, in the case of the alternator pulley unit with a built-inone-way clutch of the present invention, a torque necessary for rotatingthe driven pulley 7 a relative to the sleeve 8 a in the direction togive overrun is made as small as about 0.35N·m (0.5N·m or less). Hence,in the case of this example, the elastic constant of respective springs39 constituting the one-way clutch 18, the sliding resistance of thepair of seal rings 36 a, 36 b with respect to the respective inner rings22, and the rolling rotation resistance of the pair of support bearings17 a, 17 b are respectively made not higher than predetermined values.Therefore, in the case of this example, to decrease the slidingresistance of the pair of seal rings 36 a, 36 b, the interference of theedge rims of the seal lips of the resilient members 38 constituting therespective seal rings 36 a, 36 b, relative to the inner rings 22 isrestricted to a range of approximately from 0 to 0.2 mm.

According to the alternator pulley unit with a built-in one-way clutchof the present invention constructed as described above, the one-wayclutch 18 transmits only a turning force in a predetermined directionbetween the driven pulley 7 a to which the outer ring 26 is internallyfitted and secured, and the rotation shaft 3. For example, in FIG. 2 ifit is assumed that the inner ring 20 for the one-way clutch is fixed andonly the outer ring 26 rotates, in the case where the outer ring 26rotates in the clockwise direction in FIG. 2, the respective rollers 29,based on a force received from the inner peripheral face of the outerring 26, oppose the resilience force of the respective springs 39 andtend to be displaced to the side where respective recesses 25 becomedeep. The respective rollers 29 are then able to roll inside thecylindrical gap 28, so that a so-called overrun state results wherein aturning force cannot be transmitted between the outer ring 26 and theinner ring 20 for the one-way clutch. On the other hand, when the outerring 26 rotates in the counterclockwise direction in FIG. 2, therespective rollers 29 encroach into a wedge shape at a portion where therespective recesses 25 become shallow, as shown by the two dot chainline in FIG. 2, based on a force that respective rollers 29 receive fromthe inner peripheral face of the outer ring 26 and the resilience forceof respective springs 39, thus integrally coupling the outer ring 26 andthe inner ring 20 for the one-way clutch, so that a so-called lockedstate results wherein a turning force can be freely transmitted betweenthe outer ring 26 and the inner ring 20 for the one-way clutch.

Moreover, in the case of the present invention, the torque necessary forrotating the driven pulley 7 a relative to the sleeve 8 a in thedirection to give overrun is made as small as about 0.35N·m. Therefore,if the predetermined direction is appropriate relative to the rotationdirection of the crank shaft, when the rotational speed of the engine isconstant or tends to increase, the turning force can be freelytransmitted from the driven pulley 7 a to the rotation shaft 3, and whenthe rotational speed of the engine tends to decrease, the driven pulley7 a and the rotation shaft 3 can be promptly rotated relative to eachother, thereby effecting the overrun state. As a result, regardless ofvariations in the rotational speed of the engine, the rotation of thealternator can be maintained sufficiently in the high region, to ensurethe power generating efficiency, and the occurrence of abnormal soundsdue to slipping between the driven pulley 7 a and the endless belt 15wrapped around the driven pulley 7 a, and a decrease in the life span ofthe endless belt 15 can be prevented.

Furthermore, in the case of this example, since the torque necessary forrotating the driven pulley 7 a relative to the sleeve 8 a in thedirection to give overrun is made as small as about 0.35N·m, the pulleyunit can sufficiently cope with slight variations in the turning angularvelocity which are caused during one rotation of the engine crank shaft,and when the running speed of the endless belt 15 tends to decrease, thedriven pulley 7 a and the rotation shaft 3 can be freely rotatedrelative to each other, thereby effecting the overrun condition. As aresult, according to the present invention, the pulley unit can cope notonly with variations in the rotational speed of the engine but also withslight variations in the turning angular velocity, ensuring the powergenerating efficiency of the alternator, as well as enabling theprevention of the occurrence of abnormal sounds, and of a decrease inthe life span of the endless belt.

FIG. 3 shows a second example of the embodiment of the presentinvention. In the case of this example, a pair of support bearings 41,each being a deep groove ball bearing, and a one-way clutch 18 a being aroller clutch are disposed between the outer peripheral face of thesleeve 8 a and the inner peripheral face of the driven pulley 7 a. Thepair of support bearings 41 of these comprises, respectively, an outerring 43 having a deep groove outer ring raceway 42 on an innerperipheral face, an inner ring 45 having a deep groove inner ringraceway 44 on an outer peripheral face, a plurality of balls 46 beingrolling bodies disposed so as to be freely rollable between the outerring raceway 42 and the inner ring raceway 44, a bearing retainer 33 afor holding thee balls 46 so as to be freely rollable, and a pair ofseal rings 47 disposed between the inner peripheral face at opposite endportions of the outer ring 43 and the outer peripheral face at oppositeend portions of the inner ring 45. These respective support bearings 41are disposed between portions near the opposite ends on the outerperipheral face of sleeve 8 a and portions near the opposite ends on theinner peripheral face of the driven pulley 7 a, by internally fittingand securing the outer rings 43 by interference fit to portions near theopposite ends on the inner peripheral face of the driven pulley 7 a, andexternally fitting and securing the inner rings 45 by interference fitto portions near the opposite ends on the outer peripheral face of thesleeve 8 a. Additionally, the outer peripheral rim portions of therespective seal rings 47 are secured on the inner peripheral faces atthe ends of respective outer rings 43, and the inner peripheral rimportions thereof are slidingly contacted with the outer peripheral facesat the ends of the respective inner rings 45.

Moreover, the one-way clutch 18 a is disposed between the intermediateportion on the outer peripheral face of the sleeve 8 a and theintermediate portion on the inner peripheral face of the driven pulley 7a. In the case of this example, the axial length of an outer ring 48 forthe one-way clutch constituting the one-way clutch 18 a is made shorterthan that of the outer ring 26 (FIGS. 1, 2) in the case of the firstexample described above, thereby making the outer ring 48 for theone-way clutch separate from the outer rings 43 constituting the pair ofsupport bearings 41. The inside faces of the outer ring side brimportions 27 a, 27 b disposed at axially opposite ends of the outer ring48 for the one-way clutch are respectively made to face the end faces ofthe clutch retainers 30. In addition, in the case of this example, thetorque necessary for rotating the driven pulley 7 a relative to thesleeve 8 a in the direction to give overrun is made as small as about0.25N·m (0.3N·m or less).

According to the structure in this example constructed as describedabove, the torque necessary for rotating the driven pulley 7 a relativeto the sleeve 8 a in the direction to give overrun is made about0.25N·m, which is even smaller than the case of the first exampledescribed above. Hence, the pulley unit can further cope with slightvariations in the turning angular velocity of the crank shaft, comparedto the case of the first example. Moreover, according to the structurein this example, even if the tension of the endless belt 15 (see FIG. 6)decreases to about 30 kgf, the pulley unit can follow the variations inthe turning angular velocity to ensure the power generating efficiencyof the alternator, as well as enabling the prevention of the occurrenceof abnormal sounds, and of a decrease in the life span of the endlessbelt 15.

Other construction and operation are similar to those in the case of thefirst example described above. Hence similar parts are denoted by thesame symbols and repeated description thereof is omitted.

FIG. 4 shows a third example of the embodiment of the present invention.In the case of this example, differing from the case of the secondexample described above, the respective support bearings 41 a areprovided with the seal rings 47 disposed only on one end portion on theside closer to the axially opposite ends of the driven pulley 7 a andthe sleeve 8 b. Hence, in the case of this example, the slidingresistance of the seal rings 47 in the whole pulley unit can be reduced,enabling a decrease in the torque necessary for rotating the drivenpulley 7 a relative to the sleeve 8 b in the direction to give overrunto about 0.20N·m (0.3N·m or less), which is even smaller than the casein the second example described above. Moreover, in the case of thisexample, small diameter portions 49 are formed on the outer peripheralface at opposite ends of the sleeve 8 b. When the respective inner rings45 constituting the respective support bearings 41 a are externallyfitted and secured by interference fit, on the respective outerperipheral faces of the sleeve 8 b, axial displacement of the respectivesupport bearings 41 a relative to the sleeve 8 b can be prevented byabutting one end face of the respective inner rings 45 against steppedportions 50 being a continuous portion of the small diameter portion 49and the body portion.

Other construction and operation are similar to those in the case of thesecond example described above. Hence similar parts are denoted by thesame symbols and repeated description thereof is omitted.

Incidentally, in the case of the respective examples described above,the description has been given of a structure where the one-way clutchis a roller clutch using rollers as a plurality of lock members.However, the present invention is not limited to such a structure, andis also applicable to a structure wherein the one-way clutch is a spragone-way clutch using sprags as the plurality of lock members.

Since the alternator pulley unit with a built-in one-way clutch of thepresent invention is constructed and operates as described above, thepower generating efficiency of the alternator can be ensured, and theoccurrence of abnormal sounds, and a decrease in the life span of theendless belt can be sufficiently prevented. As a result, a reduction insize of an alternator incorporating this pulley unit can be realized.

What is claimed is:
 1. An alternator pulley unit with a built-in-one-wayclutch comprising a sleeve that can be freely externally fitted andsecured to a rotation shaft of the alternator; a driven pulley disposedconcentric with the sleeve around the sleeve; a one-way clutch providedbetween an axially intermediate portion on an outer peripheral face ofthe sleeve and an axially intermediate portion on an inner peripheralface of the driven pulley, which can freely transmit a turning forcebetween the driven pulley and the sleeve, only when the driven pulleytends to rotate relative to the sleeve in a predetermined direction; anda pair of support bearing provided between the outer peripheral face ofthe sleeve an the inner peripheral face of the driven pulley to hold theone-way clutch from the axially opposite sides, which enable freerotation of the sleeve and the driven pulley relative to each other,while rotatably supporting a radial load applied to the driven pulley,wherein a torque necessary for rotating the driven pulley relative tothe sleeve in the direction opposite to the predetermined direction islimited up to 0.5N·m.
 2. The alternator pulley unit with a built-inone-way clutch of claim 1, wherein the torque necessary for rotating thedriven pulley relative to the sleeve in the direction opposite to thepredetermined direction is 0.3N·m or less.
 3. The alternator pulley unitwith a built-in one-way clutch of claim 2, wherein the pair of supportbearings are ball bearings.
 4. The alternator pulley unit with abuilt-in one-way clutch of claim 1, wherein the pair of support bearingsare ball bearings.